The present invention relates to translation of sentences expressed in a natural language into corresponding sentences expressed in another natural language, and more particularly to a method and an apparatus for carrying out the translation.
Although the present invention can be applied to translation between any of a plurality of natural languages, it is assumed in the following that the invention is applied to translation of English sentences into Japanese sentences and vice versa for the convenience of description.
Methods for machine translation and translators heretofore proposed or commercially available may be categorized into three classes as follows:
The first class includes those translators which are destined for translation of English words (or Japanese words) into Japanese words (or English words), i.e. those serving for storage of words or dictionaries, so to speak.
The second class includes those translators destined for translation of relatively simple sentences, such as sentences manipulated as a whole and frequently used sentences (e.g. "How are you?", etc.). Those translators which perform translation by replacing some words constituting parts of a sentence by other words also belong to this second class.
The third class includes those translators which can perform translations between complex sentences of given patterns by parsing. A typical one belonging to this class is disclosed in Japanese Laid-Open Patent Application No. 102071/1980.
Among the translators belonging to the second class mentioned above, commercially available handy translators for travellers' in foreign countries are one example.
The handy translator of this type stores therein the frequently used sentences classified into sections such as "In Plane", "At Restaurant", "At Customs" and so forth in accordance with situations which the traveller will encounter. In use, the traveller first selects the section which he desires to confer with by operating associated keys. Next, upon actuation of a search key, sentences which are frequently used in the situation corresponding to the selected key are sequentially displayed one after another. When a sentence of interest which the traveller wants to use is displayed, a translation key is operated, whereupon a translated sentence corresponding to the selected sentence is displayed.
The handy translator of the type described above is in principle substantially same as those belonging to the first category in respect to the fact that pairs of the frequently used Japanese sentences and corresponding English sentences are previously stored in a memory, wherein the sentence as required on occasion is selected to be displayed in a corresponding English (or Japanese) expression.
Accordingly, in order to make it possible to translate a great variety of sentences, not only a memory of an enormously great capacity is required, but also the procedures for selecting a sentence to be translated become much more complicated, to a great disadvantage.
In the case of the translator machine or apparatus belonging to the third category described above, an English text inputted to the translator apparatus is translated into a sentence of a target (output) language through processes of parsing and retrieval of correspondent or target words by resorting to the dictionary access, as is described in the Japanese Laid-Open Patent Application No. 102071/1980 cited above. The translator apparatus of this class can certainly deal with translations of numerous sentences of various patterns. However, it requires a high-speed computer of a large scale, involving great expense and thus providing obstacles to the common use on a home basis.